1. Field of the Invention
The present invention relates to a multi-point connected conference system for use when a plurality of remote conference rooms are connected to perform conference, and the like, particularly to the voice control of a conference terminal control device.
2. Description of the Prior Arts
A remote conference system for exchanging voice information among a plurality of terminals installed in remote locations has heretofore been known, and FIG. 1 shows a constitution block diagram of a multi-point control unit (hereinafter referred to as MCU) as one example of such conference terminal control device disclosed in Japanese Patent Application Laid-Open No. 149441/1996.
As shown in FIG. 1, MCU 100 comprises a demultiplexer (shown as DEMUX) 2 for separating voice information transmitted from any of conference terminals 30A(1) to 30A(m) installed in remote locations into a compressed voice code and a voiced/unvoiced code, a speaker detection circuit 4 for detecting a speaker based on the voiced/unvoiced code of each terminal, a first selector 6 for selecting only the voiced code from the compressed voice codes from any of the conference terminals 30A(1) to 30A(m), a decoder 8 for decoding the compressed voice code selected by the first selector 6, an attenuation circuit 10 for adjusting a decoded voice level, a synthesizing circuit 12 for synthesizing an output voice signal of the attenuation circuit 10, an encoder 14 for compressing the synthesized voice signal, a distribution circuit 18 for distributing the compressed voice code and other outputs of the encoder 14 to all conference terminals 30B(1) to 30B(m), and other components. Here, n decoders 8 and n attenuation circuits 10 are provided for m conference terminals in which there is a relation of mxe2x89xa7n. The demultiplexer 2 comprises m demultiplexers 2(1) to 2(m), the decoder 8 comprises n decoders 8(1) to 8(n), and the attenuation circuit 10 comprises n attenuation circuits 10(1) to 10(n).
In MCU 100, upon receiving the voice information from any one of the conference terminals 30A(1) to 30A(m), the speaker detection circuit 4 judges the compressed voice code from which one of the conference terminals is voiced information on the voiced/unvoiced code separated by the DEMUX 2, and the first selector 6 selects the conference terminal according to the judgment result, and supplies the compressed voice code of the conference terminal to the decoder 8.
For example, when it is judged that the conference terminals 30A(1) and 30A(3) are voiced among all the conference terminals 30A(1) to 30A(m), the first selector 6 supplies the compressed voice codes from the conference terminals 30A(1) and 30A(3) to the decoders 8(1) and 8(2), respectively.
Subsequently, the decoder 8 decodes the compressed voice code to generate a voice signal, and the attenuation circuit 10 adjusts the level of the voice signal, and transmits the signal to the synthesizing circuit 12. The synthesizing circuit 12 adds/synthesizes a plurality of voice signals from the attenuation circuits 10(1) to 10(n), and transmits the signal to the encoder 14. The encoder compresses the synthesized voice signal and transmits the signal to the distribution circuit 18. The distribution circuit 18 transmits the compressed voice signals to all of m conference terminals 30B(1) to 30B(m).
In the conference using the above-described conference terminals, a state in which there is only one speaker is frequently generated. Even in such a state, the MCU 100 detects the conference terminal, passes the speaking through the decoder 8, the attenuation circuit 10, synthesizing circuit 12, and the following circuits, and performs the voice decoding, level adjustment, voice compression processing, and so on for speaking during the conference.
However, such voice processing is necessary only when speech inputs from a plurality of conference terminals are simultaneously generated, and are essentially unnecessary when only one person speaks. Therefore, for only one speaker, the decoding, attenuating and other processes waste power. Moreover, since the compressed voice is decoded, and the decoded voice is compressed again and distributed to the conference terminals, the sound quality transmitted to each conference terminal is deteriorated in some cases.
An object of the present invention is to provide a conference terminal control device which simplifies a procedure of a voice processing, reduces power consumption necessary for the processing, and enhances a sound quality to present easily audible voices in a conference.
According to the present invention, to solve the above-described problems, the conference terminal control device is constituted as follows:
Specifically, when the number of voiced conference terminals is one, or equal to or less than a predetermined number, synthesis processes of a compressed voice code from the conference terminal which are usually performed, that is, decoding, attenuating, synthesizing, compression, and so on are omitted, and the code is directly transmitted to each conference terminal. This can reduce redundant decoding/compression processes, and can prevent wasteful power consumption and processing, and sound quality deterioration.
Specifically, a voiced or unvoiced code is attached to the voice code from the conference terminal, and the conference control terminal control device reads this voiced or unvoiced code from the voice code from the conference terminal to detect the voiced conference terminals and measure the number of voiced conference terminals. If the number is two or more than a predetermined number, then the voice code from the conference terminal is passed through a decoder, an attenuation circuit, a synthesizing circuit, and so on to process, synthesize, code and distribute the voice code of each conference terminal to each of the conference terminals in the same manner as in the conventional art. On the other hand, if there is only one or less than the predetermined number of the conference terminals, then, the voice code from the conference terminal is directly transmitted to the distribution circuit and distributed to the conference terminals without passing through the processing processes.
Therefore, there is provided a conference terminal control device, comprising conference terminals installed in a plurality of locations, a decoder for decoding compressed voice codes from the conference terminals, attenuation circuits for adjusting decoded voice levels outputted by the decoders, a synthesizing circuit for adding/synthesizing output voice signals of the attenuation circuits, an encoder for compressing a voice signal outputted by the synthesizing circuit, and a distribution circuit for distributing a compressed voice code to the conference terminals so that the conference terminals are interconnected, characterized in that a multi-point control device comprises a demultiplexer for separating voice information from any of the conference terminals into the compressed voice code and a voiced/unvoiced code; a speaker detection circuit for detecting whether the compressed voice code is voiced or unvoiced based on the voiced/unvoiced code and measuring the number of voiced conference terminals; a first selector for, when the measured number of voiced conference terminals from the speaker detection circuit is more than a predetermined number, connecting the detected voiced conference terminal to the decoder and for, when the measured number is equal to or less than the predetermined number, connecting the detected voiced conference terminal to a second selector; and the second selector for, when the measured number is more than the predetermined number, selecting the encoder, for, when the measured number is equal to or less than the predetermined number, selecting the first selector, and for outputting the compressed voice code from either one of the selected encoder to the distribution circuit.
When the number of voiced conference terminals determined by the speaker detection circuit is one, or equal to or less than the predetermined number, the first selector selects the connection with the second selector, and transmits the compressed voice code from the conference terminal to the second selector. The second selector selects the connection with the first selector, and transmits the compressed voice code directly transmitted from the first selector to the distribution circuit, and the compressed voice codes are distributed to the conference terminals.
On the other hand, when the number of voiced conference terminals determined by the speaker detection circuit is two, or more than the predetermined number, the first selector selects the connection to the decoder, and connects the voiced conference terminal to the decoder. The second selector selects the connection with the encoder. Thereby, the compressed voice code from the voiced conference terminal is transmitted to the decoder, decoded in the decoder, and attenuated to have a predetermined value by the attenuation circuit. The voice signals are synthesized by the synthesizing circuit. Subsequently, the signal, after being encoded by the encoder, is transmitted to the distribution circuit via the second selector. The distribution circuit transmits the codes to each conference terminal.
As described above, when the number of speakers is one, or equal to or less than the predetermined number, the compressed voice code is directly distributed to each conference terminal. Therefore, a wasteful processing is not performed midway, and deterioration of sound quality and other disadvantages by the processing are not caused.